This invention relates to a multi-engine plant comprising a plurality of turbocharged internal combustion engines, of which at least one is intended to operate in stand-by mode during a substantial part of the plant's operating time while simultaneously another engine operates on load, each of said engines having an individual charging air system.
In this context an engine operating in stand-by mode means an engine that idles for extended periods of time, i.e. runs unloaded, or at low load, for instance not exceeding about 25% of the maximum output.
Said mode of operation--which one would generally seek to avoid--occurs in connection with self-contained power plants, i.e. plants independent of external energy sources, requiring a high degree of security of continuous energy delivery. Such power plants are typically used on board ships, drilling platforms and in connection with other units isolated with a view of energy.
In order to make sure that the actual needs for energy delivery can be met at any working conditions, it is necessary, and generally obligatory, to provide the plant with a number of additional or auxiliary engines, which on occasion, and possibly then at rather short notice, shall be able to contribute to, and possibly fully take over the delivery of energy.
Due to the fact that the power plants in question are often automatic, and thus periodically unmanned, the energy delivery criterion implies that the auxiliary engines shall run continuously, meaning that they mainly operate in stand-by mode.
As mentioned above this mode of operation is undesirable because it involves various problems of which the most severe are: Low temperature corrosion and contamination of air and gas passages by blowback of exhaust gas. Concurrent with decreasing load the last mentioned problem becomes more and more predominant until the exhaust gas pressure finally exceeds the charging air pressure, following which the insufficient charging air pressure incontestably is the main cause of the above mentioned problems resulting from stand-by operation.
Under these circumstances it is necessary to increase the charging air pressure and it is known to do so by means of an electrically driven auxiliary blower. Due to various reasons said solution is, however, not optimum. It necessitates the presence of and investment in comparatively expensive blowers etc. and from the energy aspect it does not constitute an optimum solution for the plant as a whole.